Semiconductor light sources such as light-emitting diodes have become increasingly interesting for lighting applications over the last few years. The reason for this is, among other things, that significant technical innovations and great progress has been achieved both with the brightness and the light efficiency (light output per watt) of these light sources. Not least thanks to the comparatively long service life, light-emitting diodes were able to develop into an attractive alternative to conventional light sources such as incandescent lamps or gas discharge lamps.
Semiconductor light sources are well known from the state of the art and are referred to as light-emitting diodes hereinafter. In the following, this term shall comprise both light-emitting diodes from inorganic materials and light-emitting diodes from organic materials. It is known that the light emission of light-emitting diodes correlates with the current flow through the light-emitting diodes. For brightness control, light-emitting diodes can be controlled through an operating unit. In a portable operating unit with a battery, such as a smart phone, the life of the battery is very limited and constitutes a significant problem. Charging the battery is principally accomplished over a wired connection with a charging unit. Besides the charging unit, charging also requires a suitable power supply, such as a power socket, to achieve a successfully charge the battery.
The present invention provides a circuit and a method that takes this situation into account, and that enables a specific modification of the light emission characteristics, for example based on charge of a battery for a wireless operating unit.